Swim bladder disease

This is a discussion on Swim bladder disease within the Tropical Fish Diseases forums, part of the Freshwater Fish and Aquariums category; -->
I have done some research on the symptoms that my platy is having and this is the closest I've come to an answer. He ...

I have done some research on the symptoms that my platy is having and this is the closest I've come to an answer. He is 3 months old and still very tiny. His 2 siblings are growing fine. Recently he has started staying on the bottom. He does come to the top for food, but he seems to have a hard time getting and staying there. Also, his tail is pointed down. I've tried changing food (blood worms), he seems to be too tiny to eat them, same with the pea. I also tried the Epsom salt thing. It seemed to work, but now he is back to struggling. What do I need to do now? Thanks.

I honestly have no idea. I'm new to the aquarium world. I guess just because the other two fish are fine I should not assume that the parameters are fine. I'm going to go to Petco today and get what I need to test.